I'm running a bit of a sleep deficit right now because we had two clear days and nights here just as Mare Orientale, the "Eastern Sea" which usually hovers barely in view on the lunar limb, had a very favorable libration.

[Libration is the wobble of Luna on its axis which allows us to sometimes see features over the limb which are normally turned away from our line of sight. Mare Orientale is on the SW limb, and the southern and western hemisphere libration has been almost at maximum.]

The Orientale impact basin is huge, about 600 miles/1000km in diameter. I have sketched it twice before and know there is a lot of detail to be seen so I chose to use graphite pencil on white paper because I have more experience with that media. I wasn't prepared for how much detail the favorable libration and good seeing and transparency would reveal.

I started the drawing Tuesday morning and soon realized I wouldn't be able to finish it so I anchored the sketch with the main features (which I knew wouldn't change) and trusted in the National Weather Service forecast for clear skies the next 24 hours.

That forecast held and I was able to get back to work, using the "template" of the main features as a starting point. Still, there was more detail than I could render. I worked the second morning until well after local daybreak--I didn't need a light the last hour. Altogether, I spent 3 hour and 45 minutes at the eyepiece and another couple of hours tweaking the drawing and processing it with the computer. I have a good six hours in the sketch so far and I want to post a labelled version as soon as I get the time. I don't begrudge a minute of it, though--the view was the best I've ever had.

I used HB, 2B, and 6B graphite pencils, blending stumps, and my fingers on white recycled Artagain sketch paper. I've done more computer processing on the sketch than I usually do. The scan was light, so I adjusted the gamma. The SCT gives a mirror reversed view, so I digitally flipped it horizontally. I used the paintbrush function to make the background black and the foreground gray and then used smudge on the foreground to blend it. And of course I added the text. I'd like to use this pencil sketch as the basis for another sketch using black paper and Conte' crayon to give myself more practice with those media.

I've tried to make this sketch as accurate as possible, but I left much out. I know it is unusual to spend two days sketching a lunar feature, but I thought I could get away with it since MO was in full sun both days--you be the judge. Comments, feedback, and criticism are welcome.

I had to go looking for it but I remember a recent good image of Mare Orientale on LPOD. It was not so recent (more than a year ago). You'll find it on the LPOD site for July 2, 2008.lpod.wikispaces.com/July+2,+2008

Nice sketch work of this unique feature I had forgotten that it is always seen at the moons limb edge. I remember reading years ago that we see only a low shallow view of it at the moons horizon, as it resides on the 40% side of the moon never completely facing us. You have captured the major features in stark contrast of Mare Orientale as a useful tutorial.

I saw an issue of S & T some years ago that directed the observer to note the flattened limb when viewing this feature during certain phases of the libration. It appears that you have rendered this important and unique feature of the slightly flattened limb in your sketch.

Thanks for sharing this; I've learned from your sketch that I was rendering some of the subtle lines of Orientale on my full moon sketches but had forgotten what those dark concentric lines were.

Thanks for your description on how you were able to accomplish this over a two-day span. Your hard work certainly paid off on this study!

Just for the sake of showing others the differences in librations, as well as how accurate your sketch is on rendering the Orientale features that can be very allusive even on favorable librations, I'm including a comparison of images I took of Orientale over a 3 day span.

Thanks so much, everyone. Your comments are appreciated--you all know the feeling of involvement you get when you put a lot of time and energy into one of these projects.

Frank, thanks for the link to that great photo by that team of imagers--very impressive

Erika, I remember when you took those pics--a very good example of the difference in libration. In the left hand image, the dark Mare has moved into view noticeably. The difference in angle is also easily seen by looking at the shape of dark Grimaldi.

I have attached a labeled version of my sketch (I think it's accurate). As was mentioned on the LPOD link, Crater Kopff is at longitude 90Â° so that gives you an idea of how much extra lunar surface has wobbled into view.

Attached Files

This is a awesome sketch of Mare Orientale and environs! It's so great to see the multi-ringed basin in favorable libration. You've done a wonderful job rendering the basin's rings, mare and lava lakes. I get a kick out of seeing the Inner and Outer Rooks as mountains right on the limb. Michael, I saw your sketch in the Lunar Observing Forum and thought of the complimentary aspects of sketching and imaging. This is truly an exceptional drawing and I'm so delighted that you were able to share your Two Days at Mare Orientale with us.

Michael, I saw your sketch in the Lunar Observing Forum and thought of the complimentary aspects of sketching and imaging.

Rich, this has been a rewarding observation to compare to images made around the same time--very educational, too. And I think it encourages imagers to look at their pictures very closely.

Jim Mosher has been kind enough to compare my drawing to images made by others and by spacecraft in lunar orbit to help identify certain features. I have edited a couple of the labels based on his expertise.